Show the http service registered aliases

[ogattaz]

Add a remote command "cohorte:httpaliases" able to return the list of the existing aliases managed by the http service.
In the Felix world, the agent behind the command have to retrieve the service property "alias" of the "servlet" registered services.
The result of that command should be shown in the "isolate dialog" of the web admin.

@see http://felix.apache.org/documentation/subprojects/apache-felix-http-service.html#using-the-whiteboard